To prepare a well-oriented ScAlN piezoelectric film with a high piezoelectric coefficient, several groups of ScAlN films were prepared by pulse-DC reactive magnetron sputtering. The effects of gas ratio, power, substrate temperature, buffer layer, and dope rate were investigated through a control variate method. X-ray diffractometer (XRD), scanning electron microscope (SEM), and piezoelectric coefficient tester were used for characterization. The results show that the film prepared with AlN/Ti/Pt has a lower FWHM in rocking curve (2.38°) compared with the buffer layer of Ti/Pt (2.62°). The principle of scandium doping was briefly discussed. The ScAlN film prepared in this study has a longitude piezoelectric constant d33 of -10.5 pC/N, which is 0.9 times higher than that in pure AlN. XRD patterns and SEM images reveal that the improvement in piezoelectric constant is caused by the distortion of the lattice rather than a transition in the crystal structure.